Pre-season friendlies tend to be as reliable as zodiac signs when it comes to telling the future but, even with that caveat, Arsène Wenger was rightfully encouraged by this exuberant victory. Yaya Sanogo scoring four in a match after failing to find the net at all last season looks pretty good as omens go and the margin of Arsenal’s win was fair reward for a vibrant attacking performance in which Aaron Ramsey sparkled and Joel Campbell announced his return from loan with an artful strike.

“It is very difficult to draw any conclusions after a game like that. Benfica might be on a different level of preparation,” Wenger said. “But for important periods of the game we played the way we want to play. Our game is based on movement, technical skill and togetherness in the final third and that’s what we did.”

The Emirates Cup, launched seven years ago, has become a piece of Arsenal heritage, a summer staple that survives while the club’s other pre-season traditions are changing: Arsenal no longer spend the build-up to new campaigns fretting about whether their squad will be picked apart by rich predators and allowing themselves to be linked with stars they will never lure. A summer spree of over £60m to date shows that the age of austerity is over and this display will reinforce the hope that the club are entering the Era of Wenger’s Vindication.

The only one of the four major summer purchases to start here was Calum Chambers, deployed at centre-back alongside Nacho Monreal in an experimental defence that included the 19-year-old Héctor Bellerín at right-back. That arrangement reflected the low stakes of the match but a crowd of nearly 60,000 was still treated to a high-paced spectacle, at least compared with the tame 2-2 draw between Monaco and Valencia earlier.

The shiniest totem of Arsenal’s new power, Alexis Sánchez, began on the bench but the £32m capture from Barcelona was acclaimed like a hero-elect when he came on in the 71st minute, even if all he showed is that he has yet to reach full fitness. Wenger says the Chilean will play for 45 minutes in Sunday’s match against Monaco as he tries to get up to speed.

By the time Sánchez was introduced the match had lost all intensity, Sanogo and Campbell having upstaged him as Arsenal blew away a Benfica side who had begun brightly.

The Portuguese exposed uncertainty in Arsenal’s improvised defence early on, Nico Gaitán hitting the crossbar from 15 yards. Campbell and Sanogo squandered good chances before the Frenchman began atoning in the 26th minute, converting from close range after being set up by a beautiful turn and cross by Ramsey.

In the 40th minute the impressive Bellerín skedaddled down the right and exchanged passes with Sanogo before calmly crossing to Campbell, who placed the ball into the bottom corner from 15 yards. The Costa Rican then prodded wide after another sweeping move but had his wits about him in the 44th minute when he received a pass from Ramsey and, rather than shoot, teed up Sanogo to make it 3-0.

With Benfica unravelling in the face of Arsenal’s passing and movement, Sanogo completed his hat-trick on the stroke of half-time, contorting as he wrestled with a defender to stab a cross from Kieran Gibbs into the net from five yards.

“That was really the goal of a quality striker,” said Wenger, who suggested that he expects a newly confident Sanogo to prove more effective back-up to Olivier Giroud in the coming season than he did last term.

“Sanogo was injured for basically two years before he came to us,” Wenger said. “He came last year on a free and we worked very hard for six months with him. From January onwards he was slowly getting better. Now that we have worked very hard we want him to stay.”

Wenger says he also intends keeping Campbell. “He has a good balance between individual skill and a collective attitude and that’s not easy to find.”

Sanogo continued making the case to trust him by netting his fourth goal just after half-time, tapping in after Artur spilled a shot from Ramsey. After many substitutions Benfica pulled a goal back as Gaitán eluded the defence to head in from a long throw-in – a no doubt unnecessary warning for Arsenal fans not to get carried away.